1. Field of the Invention
The present invention relates to the manufacture of optically delineated circuits and particularly to the curing of photoresists used in such manufacture by flash discharge arc lamps.
2. Description of the Prior Art
In the manufacture of integrated circuits, it is usual to slice a wafer from a semiconductor crystal, apply a photoresist to the surface of the wafer, illuminate the photoresist with a circuit pattern, develop the pattern (this is done by washing away the more soluble portions of the photoresist and may be either the illuminated or unilluminated portions depending on whether it is a positive or negative photoresist), curing the remaining photoresist, and treating the exposed wafer surface to form the desired circuit components and connections. The curing step is necessary to make the remaining photoresist impervious to the various treatment procedures.
For high resolution, ultraviolet sensitized photoresists are used with ultraviolet exposures. Curing is thus usually by ultraviolet also although other radiation and heat are usually present. Typical curing time has been one half hour and the curing process has produced two additional problems. One is a flowing of the photoresist reducing resolution. The other is erratic results in removal of the cured photoresist after completion of treating.
Curing or polymerization of various polymeric materials has been effected in the past with flash discharge arc lamps. U.S. Pat. Nos. 3,782,889 and 4,167,669 of the present inventor describe methods and apparatus for that purpose. In these prior patents there were no resolution requirements. Xenon flash lamps were used that normally put out energy over a broad spectrum extending both above and below the visible spectrum. Portions of the spectral output can be emphasized depending on gas mixture in the lamp, fill pressure, current density, pulse width, bore size and envelope material. High infrared output was considered the least desirable for the present purposes since the high temperatures produced could be expected to cause melting and flow while the high rate of energy input has been known in the past to cause spattering as could be expected by fast thermal expansion in discrete surface areas.